Chemical recovery process



Nov. 17, 1959 L. T. sANDBoRN ETAL 2,913,309

CHEMICAL RECOVERY PROCESS Filed May 14, 1958 2 Sheets-Sheet 1 BY @amg @wk/#M ATTORNEYS Nov. 17, 1959 L. T. SANDBORN EI'AL CHEMICAL RECOVERY PROCESS Filed nay 14, 195e 2 Sheets-Sheet 2 BROWN L /QL/OK AL/UC'LAVE' 14714 TEM/959197' Uff 0F 147' LEAST 250 C.

KE'TO/VE MFf/vABLYMEr/m Erl/YL Kiran/E) PHASE' I PHASE 2 AODUCT /f E TONE KETO/VE H07 AQUE'Ol/J HL/(AL/ METAL ALK/JL] METAL SULF/TE INVENTOR ATTORNEYS United States Patent CHEMICAL RECOVERY PROCESS Application May 14, 1958, Serial No. 735,141 39 claims.k (ci. zal- 129) This invention relates to a method for recovering or deriving inorganic, alkali metal salts from the analogous salts of nonaldehydic water-soluble carboxylic acids such as those contained in liquors resulting from alkaline and neutral pulpingV processes. More particularly, the invention relates to the production and recovery of inorganic chemicals, including alkali metals, in the form of suliites and bisullites; and organic chemicals, including relatively low molecular-,weight organic carboxylic acids, from the liquors resulting from alkaline and neutral processes for pulping .lignocellulosic materials.

vIt is known that alkaline and neutral pulping liquors contain substantial quantities of both inorganic and organic chemicals. 'Ihe inorganic materials present in such liquorsv essentially correspond to or are derived from thepulping reagents employed, whereas the organic materials are derived from the lignocellulosic material, and comprise relatively low molecular weight carboxylic acids which are present as alkalimetal salts.

In kraft pulping technology, itis conventional torecover at least some of the inorganic chemical values from the black liquor. Pursuant to routine practice the black liquor is concentrated, and burned to decompose the organic materials and form an inorganic product known as smelt from which alkali metal values are recovered, Potentially, the organic materials in alkaline and neutral pulping liquors, particularly the low molecular weight carboxylic acids including formic, acetic, lactic, glycolic and alpha hydroxy butyric acid which are present as alkali metal salts, are of marked economic and technological significance. Prior to this invention, however, the art has failed to develop a commercially accepted process for the recovery of such low molecular weight acids.

Accordingly, it is the primary object of the invention to provide a method for producing the various nonaldehydic, water-soluble carboxylic acids containing from one to about four carbon atoms from the alkali metal salts thereof. Y Y o It is an important object of the invention to provide a method for producing free nonaldehydic carboxylic acids containing from one to Yabout four carbon atoms and alkali metal sulii'tes and bisultes from the alkali metal salts of such aci-ds.

lt is a more specic object to provide a method for producing nonaldehydic carboxylic acids containing from one to about four carbon atoms from the alkali metal salts thereof present in liquors resulting 'om neutral and alkaline processes for pulping lignocellulosic materials.

It is an additional specific object of the invention to provide a method effective to produce from liquors resulting from neutral and alkaline pulping processes, both nonaldehydic carboxylic acids containing from one to about four carbon atoms and alkali metal sulfites or bisullites.l

It is an additional object of the invention to provide a method for the production or recovery of both inorganic molecular weight carboxylic acids having #PCC and organic chemical materials from the liquors from sulfate, soda, and neutral sulfite semi-chemical pulping.

It is a further object of the invention to providefa method effective to recover the alkali metal values contained in used pulping liquors including such alkali metal values as may be combined in the form of salts of low from one tol about four carbon atoms. ,a

It is a further specific object of the invention to provide a method eifective to recover as, sultes or hydrated sulfites the alkali metal values present inl used alkaline and neutral pulping liquors. 1 u

It is an additional object of the invention to provide a continuous process which entails the production of low molecular weight carboxylic acids from alkaline and neutral pulping liquors.

The invention generically comprises reacting, in aque;l ous solution, an alkali metal salt of at least one aliphatic, nonaldehydic carboxylic acid having from one to four carbon atoms per molecule with (l) bisullite ion and (2) a normally liquid aliphatic ketone capable of forming an alkali metal bisulfite addition product under the conditions to produce a first phase containing said carboxylic acid and a second phase containing an alkali metal bisulte addition product of said ketone, said alkali metal of said addition productrbeing derived from said carboxylic acid salt, and separating said first andsecond phases.

The bisulite ion reactant employed in the invention is normally formed by the introduction of sulfur dioxide or sulfurous acid into the aqueous medium in whichv the reaction is eiected. The degree to which the reaction whichv characterizesthe invention proceeds is a function of the relative proportion of bisulfite reactant utilized. Accordingly, in the preferred embodiment of the invention bisulfite ion is utilized -in an amount stoichiometrically suliicient to react with at least a major proportion of the alkali metal present in the carboxylic acid salt reactant. 4.

lt will be appreciated that the biusulfite ion may `first react with basic materials presenthin the system rather than the carboxylic` acid salt reactant. More specifically, in vsome systems initially characterized by a basic pH a quantity of bisullite ion requisite to reduce the pH to a value not greater than 7 may be consumed prior to significant reaction between the bisullite ion reactant and the carboxylic acid'salt reactant. Accordingly, the invention is preferably practiced at a pH not greater than 7, and more appropriately at a pH of from about two to about four. Neither the initial pH of the system nor the specific proportions of bisuliite ion reactant utilized are critical. Those skilled in the art will readily adjust the pH of the system and relative proportions of reactants to achieve the result desired in any specific application of the invention. i

The essential characteristic of the ketones contemplated by the invention is that of forming alkali metal bisulite addition products; Hence, the particular vketone utilized does not constitute the essence of the invention which generally embraces the utilization of all normally liquid aliphatic ketones which formV such addition products under the conditions. The art is well cognizant of those ketones which form bisuliite adducts and which are therefore contemplated. More specifically, the invention entails the utilization, inter alia, of aliphatic straight and branched chain cyclic and acyclic aliphatic ketones containing from about three to nabout six carbon atoms of which acetone, methyl ethyl ketone, methyl propyl ketone,

preferred. It is apparent that the ketones contemplated may be represented by the formulae wherein .R and R1 are aliphatic radicals and R2 represents an aliphatic radical which forms'a cyclic compound with the carbon atom ofthe keto group. As indicated in the textbook Fieser and Fieser Organic Chemistry, Zdfed., pp. 203-207, the bisuliite adducts of such ketones are understood to respond to the respective formulae SOIM and

RIC

soaM

wherein M represents an alkali metal atom. A The ketones employed in the practice of the invention arepreferably utilized at least in the amounts theoretically sufficient to form an adduct with all vof the alkali metal bistilte produced and to -supply a solvent medium for the organic acids which are produced. The specific proportions of ketone reactant do not, however, constitute an essential feature of the invention, the objectives of which are achieved, at least to some usefulextent, by the utilization ofsuch reactant in any relative proportion.

'The distribution of the free carboxylic acid product and-the'ketone adduct formed, between the two phases of the system which characterizes the reaction mixture of the invention, is Aa function of the water-solubility and hence, ofthe molecular weight and structure of the ketone reactant utilized. The two phases formed in the initial step of the process can be either a liquid `phase and a solid phase or two different liquid phases or layers, Vdepending upon the relative solubility characteristics of the ketone reagent utilized and the amount of water present. By way of example, when ketone, such as acetone, which is soluble in water in substantially all' proportions is 'utilized in asystem containing water in amount insucient to dissolve appreciable portions of the ketone-alkali metal bisulfite adduct, the adduct precipitates as a solid phase and the free carboxylic vacids appear in solution in a liquid phase containing both ketone and water.

In some applications, the efficient removal of the solid adduct, which is bulky and tends to retain, relatively large amounts of liquid, is diicult, and it is more expedient to employ a system in which two liquid phases are produced. Accordingly, in a preferred embodiment of theinvention, -particularly as applied to used pulping liquors, a higher molecular weight ketone such as methyl ethyl ketoneor methyl propyl ketone which is water insoluble or, in any v"event, substantially less water soluble than acetone is used to provide a generally nonaqueous ketone layer in which is dissolved thel low molecular weight carboxylic acids which are produced by the process of the'invention, and a second liquid phase comprisingan essentially aqueous solution of the ketone-alkali metal bisuliite adduct rather than a solid adduct precipitate.

Precise numerical limits cannot feasibly. be ascribed to the relative proportions of ketone and water which yield optimum results in the practice of the invention, inasmuch as suc'h proportions vary with the ketones employed, 'the nature of the alkali metal `values present, and the like. However, ketoneV alkali metal adducts ofthe type contemplated by the invention are known materials, which can easily `be obtained or prepared and employed in preliminary solubility determinations by lthose skilled in the art to insure the practice of the invention under conditions optimum to achieve any specific result desired. In general, in that embodiment of the invention in which two liquid layers are formed, it is essential only to provide, at some point in the process, sufficient water to retain the ketone-alkali metal adductin solution. Any adduct precipitate which may form can be redissolved Vby the addition of Water. Conversely when a solid adduct precipitate is desired, it is necessary only to reduce the water content of the system to a vdegree Arequisite to foreclose solution thereof. Those skilled `in the art will encounter no diiculty in respect to the production of two liquid phases or a` solid and a liquid phase system as may be desired. The two-phase system characteristic of the invention forecloses decomposition of the alkali metal bisulte ketone adduct by the carboxylic acid product.

The invention is generically applicable to the alkali metal salts of all water-soluble, aliphatic, nonaldehydic carboxylic acids. Aldehydic acids, such as glyoxylic acid, which react with bisulte ion to form an adduct are excluded. The invention, however, is applicable to the alkali metal salts of keto acids, including, inter alia, levulinic acid and pyruvic acid which are relatively less reactive with bisuliite ion than the aldehydic acids. 'Representative acids include: (l) monobasic saturated acids, c g., formic, acetic, propionic, butyric, isobutyric, valerie and isovaleric; (2) monobasic unsaturated acids, e.g., acrylic, crotonic, vinyl acetic and `methyl crotonic; (3) dibasic saturated acids, e.g., oxalic, malonic succinic and glutaric; (4) dibasic unsaturated acids, e.g., maleic, fumarie, methyl maleic (citraconic), methyl fumarie (mesaconic) and itaconic; (5) tribasic saturated acids, eg., tricarballylic (1,2,3 vpropane tricarboxylic); ('6) tribasic unsaturated'acids, e.'g., aconitic; (7) hydroxy acids, eg., glycolic, lactic, alpha rhydroxy isobutyric, alpha hydroxy butyric, tartronic, malic, tartaric and citric; and (8) lketo acids, e.g., pyruvic, levulinic and acetone dicarboxylic.

The invention contemplates, without limitation, 4all of the alkali lmetal salts, including speciiically the sodium, potassium and lithium salts of all of the appropriate carboxylic acids.

The invention, in its generic embodiments, is applicable to -aliphatic nonaldehydic carboxylic acid alkali metal salt solutions of all concentrations, Vincluding extremely dilute solutions such as solutions lcontaining not more than about one percent by weight'of carboxylic acidsalt, as well as to saturated and supersaturated solutionsand solutions containing other materials such as pulping liquor components. Preferably aqueous solutions vcontaining vfrom about five percent to about twenty percent by weight of carboxylic acid alkali metal salt are employed. It will be appreciated that the aqueous carboxylic acid saltsolution suppliesa substantial quantity 'of water to the system which must be considered in respect to the adjustment of relative proportions of water and ketone to provide two liquid layers or phases, or both a liquidand `a solid phase as may -be desired.

The physical conditions of'temperature and pressure do not constitute the essence of the invention 'and are limited only by factors obvious to those skilled in the art, such asthe stability ofthe various components of the process reaction mixture. Preferably Ythe invention is practiced under the prevailing ambient or atmospheric conditions. p

The phases or layers yrespectively containing the free carboxylic acids and the ketone-alkali metal bisuliite adduct lproducts of the invention are separated byconventional means such as iltration, centrifugation, decantation, or the like. `In the case of systems in which two liquid layers .or phases areformed separation in a-separatory funnel or equivalent means, or by countercurrent extraction with the ketone reactanttis appropriate. The

separated phases are useful as such and need not .be further processed for many applicatins. For example,

action.

the phase containing the ketone bisulte addition product can be employed to precipitate lignins from kraft pulping liquor. Similarly, the carboxylic acid phase is useful in industrial processes in which such acids are employed. Further processing of either or both phases or layers, to eiect recovery of the organic and inorganic materials present therein or for recycle of certain of the components thereof to the system, may beeffected.

Any of the various expedients known to the art, including -the application of elevated temperatures, alkali treatment, and the like, can appropriately be employed to process the ketone-alkali metal bisulte adduct. Pursuant to a typical appropriate procedure, the ketone-alkali metal bisulte adduct is heated to remove the ketone by distillation and provide a bottoms or residue comprising alkali metal bisulfite. Both the ketone and the alkali metal bisullite may be recycled to the system. Alternatively, the adduct may be reacted with a basic material, such as an alkali metal carbonate, bicarbonate, hydroxide or the like to produce free ketone and alkali metal sulfite. Such basic materials are suitably employed in aqueous solution or suspension at atmospheric conditions of temperature and pressure. Elevated temperatures preferably ranging between the boiling point of water and the boiling point of the ketone component of the addition product can be utilized to expedite the re- The alkali metal sulte so produced may be employed in the formation of pulping liquor or recovered as a product of the process.

The carboxylic, acid product is appropriately recovered by conventional means such as fractional distillation. In general, the expedients appropriate for recovery of the carboxylic acid products, from the appropriate phase or layer of the reaction mixture of the invention, comprise those known to be effective to isolate such acids from ketone or aqueous ketone solution. 'Y

The invention, in a preferred embodiment, utilizes, as starting materials, liquors resulting from the neutral and alkaline pulping of lignocellulosic materials and which contain, in solution, alkali metal salts of low molecular weight, water-soluble, nonaldehydic, carboxylic acids normally containing from about one to about four carbon atoms. The conventional procedures for the neutral and alkaline pulping of lignocellulose materials are conveniently designated as the sulfate process, the soda process, and the neutral sulfite process. The sulfate and soda processes employ an alkaline liquor, and the neutral sultte process a neutral liquor in the pulping procedure with the consequent production of waste liquors of analogous pH. In general, it has been observed that alkali metal, normally sodium, salts of similar low molecular I weight organic acids i.generally comprising formic acid,

acetic acid, lactic acid and glycolic acid, and alpha hydroxybutric are present in waste liquors resulting from the various pulping procedures, although the relative proportions of the salts of the individual acids may substanftially vary. For example, black liquors from the sulfate and soda pulping processes contain, in substantial proportion, the sodium salts of each of acetic, lactic and glycolic acids, whereas the waste liquors from neutral sulte pulping, contain predominantly acetic acid and only a relatively minor proportion of formic, lactic and glycolic acids.

The properties of the lignin materials extracted from the wood or pulped lignocellulosic materi-al and present in the resulting liquors also vary materially with the pulping process employed. For example, the lignin materials present in the black liquor from alkaline pulping processes, such as the sulfate and ysoda processes, are precipitated by acidification with sulfur dioxide, carbon dioxide, and the like, whereas the lignin materials in the liquors derived from neutral suliite pulping procedures are not `so precipitated, presumably by reason of the presence therein of sulphonic acid groups.

The process of this invention is effective to recover both the low molecular weight organic, acids and the .alkali metal values from the liquors resulting from all of the various procedures for the alkaline and neutral pulping lignocellulosic materials. All such liquors and mixtures thereof are therefore contemplated as starting materials for utilization in the practice of the invention. Black liquor from the sulfate pulping processV is preferred. So-called brown liquor, produced in neutral sulte pulping, is also particularly appropriate. Mixtures of black and brown liquor can be eiciently utilized.

Liquors from conventional alkaline and neutral'pulping processes are highly diluted and may be expected to contain not more than about ten to about twenty weight percent of total solids. For use in the practice of the invention it is preferred substantially to concentrate such liquors by the removal of water therefrom. It will be appreciated that the viscosity of the used pulping liquors will increase as water is removed and the solids content is increased. Accordingly, concentration is appropriately effected to a degree requisite to increase the pulping liquor solids content such that the liquor viscosity remains sufficiently low for the efficient practice of the invention, as may routinely be determined by those skilled in the art. In general, for use in the invention, pulping liquors are concentrated to a ysolids content of at least about twenty-live'and preferably from -about thirtyfive to about fifty-live weight percent. The optimum degree of concentration will, of course, vary somewhat with each specic used pulping liquor employed. It is apparent that the invention, generically extends to unconcentrated liquors from alkaline and neutral pulping processes, and does not essentially depend upon any speciiic degree of concentration.

Preferably, a substantial proportion of the lignin materials present is removed from the used alkaline and neutral pulping liquors employed in the invention. y While not absolutely essential such lignin removal results in a more eflicient process, particularly when used alkaline pulping liquors are employed, and aords a better yield of products of higher quali-ty.

Variation in the chemical nature of the lignin materials present is usedneutral and alkaline pulping liquors generally'requires distinct procedures for lignin removal be applied to each type of liquor. l

It has now been discovered that the lignin materials in used neutral pulping liquors, which are present largely as lignosulfonic acids can be effectively precipitatedby subjecting such liquors to a pressure cook, as in an autoclave, at a temperature of at least about 225 C. and preferably from about 250 C. to 300 C., under a pressure of at least about 360, and preferably from about 700 to about 1800 pounds per square inch for a time period of at least about fifteen minutes and preferably from about twenty to about thirty minutes.v Autogenous pressure at a temperature of at least 250 C. is appropriate for commercial operation.

Organic acids and carbon dioxide are developed in the pressure cooking operation such that the systemis substantially saturated with carbon dioxide and `may contain solid phase sodium bicarbonate.

The pressure-cooked liquor, subsequent to removal therefrom of solid materials which may precipitateas a result of the cooking operation, is expediently acidified with sulfur dioxide or sulfurous acid in an amount requisite to maintain the pH below five and preferably from about two to about four to convert essentiallyall of the alkali metal values present to an alkali metal bisulte, normally sodium bisulte.

Reference is made to copending Clark et al. application Serial No. 756,299 for a more detailed description of the pressure cook method for the separation of lignin solids from used liquors from neutral sulfite pulping processes.

Used' pulping liquors from alkaline pulping processes can also appropriately be subjected to a pressure cook to effect lignin solids precipitation. ln general, conditions similar to those .appropriate for the pressure cookingofused liquors from neutral pulping can be employed. Pressure cook treatment of used alkaline pulping liquors is advantageous in foreclosing or minimizing the formation of emulsions or suspensions which complicate separation ofthe ketone-bisulte adduct phase from the carboxylic acid phase ultimately formed pursuant to the process of the invention.

The lignin material present in liquors, such as black liquor, from alkaline pulping processes, are precipitated by acidication with sulfur dioxide, sodium bisulfate, carbon dioxide, and the like, as disclosed, for example, in the patentsv to Bradley vet al., 1,606,501 and 1,833,313. In general, acidification to a pH of from about seven to about nine is satisfactory to effect precipitation of substantially all of the lignin materials present in such liquors.

Alternatively, lignin is effectively removed from used alkaline pulping liquors, and particularly from black liquor, by heating a mixture of such liquor and an acidic material such as an alkali metal bisullite or bicarbonate or sulfur dioxide or carbon dioxide in an amount requisuite to provide a pH of at least about nine, preferably from about seven to about eight, to an elevated temperature of from about 70 to about the boiling point of the liquor to eifect precipitation of lignin solids. Sodium bisuliite is preferred.

The precipitation of lignin materials from alkaline pulping process liquors by acidification with sulfur dioxide or heating withan alkali metal bisulflte yields a liquor which, like sulfur dioxide treated, pressure-cooked neutral pulping liquor, contains a substantial quantity of alkali metal suliite. A salient feature of the invention, as applied to used alkaline and neutral pulping liquors, entails recovery of the major portion of such alkali metal sulite to reaction with ketone and bisuliite ion. Alkali metal sulte recovery is efficiently achieved by commingling such liquors, preferably after the precipitated lignin solids are removed, with an organic liquid which is water miscible, but in which alkali metal sultes are insoluble, to effect crystallization or precipitation of alkali metal sulte normally in hydrated form. Appropriate liquids include aliphatic alcohols containing from about one to three carbon atoms such as methanol, ethanol, propanol or the like, and the water miscible species of theketones of the type contemplated by the invention, such as acetone. The alcohols or ketones are appropriately employed in an amount requisite to provide at least about 25% by volume, preferably from about 40% to about 100% by volume, `based on the water present in 'the liquor treated. An alkaline pH, preferably a pH of from about seven to about nine is appropriate to foreclose conversion of the alkali meta sulte product to bisuliite.

Alkali metal suliite precipitation is preferably effected with acetone which yields the alkali metal suliite product in the form of a hydrate largely free from contamination. Sodium sulfite is precipitated by acetone as a substantially uncontaminated heptahydrate. Consequently, in a process in which an alkali metal sulte is to be removed as a solid prior to adduct formation, the use of acetone in the sulte removal stage and a higher molecular Weight substantially Water immiscible ketone, such as methyl ethyl ketone to provide two liquid layers in the adduct 'formation stage is a preferred procedure. In such a process, at least some acetone will be present in the liquor which is reacted, in the adduct formation step, with the higher molecular weight ketone and bisulte ion. Accordingly, a mixture of` ketones is recovered from the respectivephases of the reaction mixture which Vis produced. Such a mixture of ketones is appropriately recycled to the adduct formation stage of the process.

Alternatively, thealkali metal suliite values may be recovered by concentration of the treated liquors to a degree requisite to elfect .precipitation thereof. By such expedient the alkali metal values are recovered as unhydrated salts.

The process of the invention can be .practiced either on a continuous or a batch basis and with or without recycle of bisultite ion, as illustrated in'the drawings, in which:

Figure 1 is a schematic flow diagram representative for the practice of the invention with recycle of bisulte ion in such a manner that all of the alkali metal in the recovered sultlte is derived from the used pulping liquors, and

Figure 2 is a schematic flow diagram representative of one method for the practice of the invention in a manner such that part of the alkali metal in the recovered sultite is supplied from other sources.

Pursuant to the continuous procedure represented in Figure l, used liquor from an alkaline or neutral pulping process, which is preferably concentrated to at least about 25% by weight solids is subjected to a preliminary treatment including addition of recycled alkali metal bisuliite to convert the alkali metal values not chemically combined with carboxylic acids to alkali metal sulfites and to elfe-ct removal therefrom of a substantial portion of the lignin materials present, adding acetone to the delignied liquor and removing the precipitated alkali metal sulte; and thereafter reacted with a ketone and bisul-fite ion to produce a two-phase reaction mixture containing in the first phase low molecular organic acids and in the second phase a ketone-alkali metal bisulfite adduct.

Referring to the step of lignin removal it is desirable to supplement the bisulte ion of the recycled alkali metal bisullte by addition of an amount of sulfur dioxide to bring the pH of the solution to about 7-9, thereby assuring conversion of most of the alkali metal values, not chemically combined with carboxylic acids, to alkali metal sullites. While it is desirable to avoid an excess of bisulte ion at this stage in the process, the process is still operable if some bisuliite ions are present and if the pH is -below the desired range, because acetone added in the next step will react with such bisulite ions to form an adduct, thereby bringing the pH back to a range typical of alkali metal sulite solutions. The addition of acetone serves both the function of precipitating the alkali metal sultite and of adjusting the pH of the solution by reacting with the acidic bisulte to produce a neutral adduct.

After the alkali metal sulte is removed the solution is saturated with sulfur dioxide and recycle ketone is added to produce a two phase reaction mixture which is separated as shown in the figure and processed to obtain a free low molecular weight carboxylic acid product, and to provide alkali metal bisulte and free ketone for recycle to the continuous process as indicated.

In some cases, it is preferable to recover, rather than to recycle, the alkali metal bisuliite to prevent an accumulation of unidentied organic acids in the system. In such cases, the noncontinuous procedure represented in Figure 2 may prove more advantageous.

ursuant to the noncontinuous method represented by Figure 2, liquor from a pulping process, preferably concentrated to a solids content of at least about 25% by weight, is subjected to a pressure cook as in an autoclave at a temperature of at least about 250 C., to effect the precipitation of lignin solids and thereafter treated with sulfur dioxide in an amount requisite, to convert substantially all of the alkali metal values to alkali'metal bisulites. Addition of sulfur dioxide sufcient to provide a pH of about two to four is generally appropriate.

The precipitated solid lignin materials are removed, and the filtrate which, in the procedure shown in Figure 2, contains bisulte ion is commingled with a ketone, preferably methyl ethyl ketone and additional sulfur dioxide, if necessary, to form a reaction mixture comprising a first liquid phase comprising an aqueous solution of the ketone bisulte addition product and a second liquid phase comprising a methyl ethyl ketone solution of low molecular weight carboxylic acids which may be separated in any appropriate manner. In the noncontinuous process illustrated in Figure 2, the bisulte addi? tion product may be reacted with an alkali, such as hot, aqueous, alkali metal carbonate to effect ketone recovery and produce an alkali metal suliite product, which is useful for example in the production of fresh pulping liquor for the neutral sultite process.

The following examples comprise the best mode presently known for the practice of the invention:

Example I An aqueous solution containing the sodium salts of 1.5 grams tartaric acid, 1.3 grams malic acid, 1.2 grams succinic acid, and 1.7 grams aconitic acid is concentrated to a volume of about l ml. and combined with 75 ml. of acetone and an excess of sulfur dioxide. The solid acetone bisulfte adduct which forms is separated from the solution and washed by moistening with 2 ml. of water, adding 50 ml. of acetone and an excess of sulfur dioxide and filtering. Soda analyses show 3.96 grams NaOH in the adduct as compared with 0.16 gram NaOH in the acetone solution. Since 96% of the soda is in the adduct, practically all of the organic acids must either be in the acetone as the free acid or associated with the solid adduct. By means of paper chromatographic methods, it is found that practically all of the acids are in the acetone solution. This fact is demonstrated in several tests. For example, with equal quantities of the acetone solution and a sample of a standard solution that contains the acids in the same concentration as in the original solution, both solutions give spots of equal size and intensity. A solution prepared by decomposing the adduct with sulfuric acid shows no trace of any of the acids with an amount four times as large as the standard. With an amount ten times as large as the standard, a solution prepared from the adduct gives a spot for tartaric acid equivalent to the standard but none of the other acids is detected. These tests show that at least 90% of thetartaric acid and practically al1 of themaleic, succinic, and aconitic acids are liberated from their salts and recovered in the acetone solution.

Analogous results are obtained when methyl ethyl 'ketone is utilized in lieu of acetone, with the exception that a water solution of adduct, rather than a solid adduct is formed, and the free acids are partitioned into the methyl ethyl ketone phase, rather than a water phase. Comparable results are also obtained with lithium and potassium salts of tartaric, maleic, succinic, and aconitic acid.

Example 1I An aqueous solution containing 1.9 grams citric acid, 1.2 grams maleic acid, 0.9 gram lactic acid, and 1.3 grams itaconic acid as their sodium salts is treated as describedin Example I to produce the acetone bisulite adductV and an acetone solution of the free organic acids. Soda analyses show 3.3 grams NaOH in the adduct and 0.1 gram NaOH in the acetone solution. Paper chromatographic tests like those described in Example I show that 90% or more of each of the acids is recovered in the acetone. In comparison with a standard, equal amounts of acetone solution and the standard give spots of equivalent size and intensity for each of the acids. In comparing the acetone solution with. one prepared from the adduct, no acids are detected in the adduct solution when equal volumes of acetone and adduct solution are used. When the amount of the adduct solution is four times that of the acetone solution, a faint spot is observed for citric acid but no other acids are detected for the adduct solution. It takes ten times as much of the solution of the adduct as of the standard to produce equivalent spots on a paper chromatogram, indi- -eating that about y% of thel citric acid precipitates with '10 or is absorbed on the adduct. These tests show that about 90% of the citric acid and practically all of the maleic, lactic and itaconic acids are recovered in the acetone solution. Comparable results are obtained with potassium salts of the carboxylic acids in lieu of sodium salts.

Analogous results are obtained with methyl ethyl ketone and with methyl-propyl ketone, with the exceptions as described in reference to the use of methyl ethyl ketone in Example I.

Example Ill A solution containing approximately one gram of levulinic acid as its sodium salt is concentrated and treated as described in Example l for recovery of solid sodium bisulte adduct and an aqueous acetone solution of levulinic acid. Soda analyses show 0.55 gram NaOH in the adduct and only 0.026 gram NaOH in the acetone solution. Paper chromatograms show that there is free levulinicacid in the acetone solution in approximately the same quantity as was present at the start.

No levulinic acid is detected in a solution of the adduct.

Example IV A solution containing 1.34'grams of sodium oxalate is treated as described Vin Example I for recovery of solid sodium bisulte adduct and recovery of an aqueous acetone solution ofoxalic acid. In this case, soda analyses show 0.786 gram NaOH in the adduct and 0.031 gram NaOH in the acetone. There is evidence of the presence of some oxalic acid or perhaps sodium acid oxalate (NaHC2O4) in the solid adduct. Nevertheless, at least a third of the oxalic acidr originally present is found in the acetone solution.

Example V An aqueous solution containing 1.76 grams of tricarballylic acid (1, 2, 3, propane tricarboxylic acid) and 1.04 grams of alpha hydroxybutyric acid as their sodium saltsY is concentrated to a volume of about 15 ml. and is treated with ml. of acetone as described in Example I to produce the acetone bisulte adduct and an acetone solution of the free organic acids. Soda analyses show 1.4 grams NaOH in the adduct and 0.2 gram NaOH in the acetone solution. Paper chromatographic tests like those described in Example I show at least of each of the acids to be present in the acetone solution.

In Examples I-V, the method of paper chromatography is essentially that of Jones, Dowling, and Skraba, Anal. Chem. 25, 394 (1953). Descending development for 16 hours on Whatman No. l -paper is used. The developing solvent consists of the organic phase obtained by mixing 200 m1. of 2ethyl1butanol with 300 ml. of aqueous 5 molar formic acid. The aqueous phase yfrom this mixture is placed in the bottom of the developing tank in order to keep the ternary system in equilibrium during development. Detection of spots is accomplished by drying the papers and spraying with an alcohol solution of brom phenol blue. The acids show up as yellow spots on a blue background. Standards for comparison consist of 0.1 molar solution of the known acids. In the instant case, the acetone solution and the solution derived from the adduct are made to a volume such that each would be 0.1 molar if it contained all the acid that had been present in the original mixture. If the solution being tested and the standard both give faint spots, it is indicated that both contain the same amount of acid. Consequently, the concentration ofthe acid in the solution can be determined by iinding how much of the solution has to be used to produce a spot equivalent to that obtained from the standard. If it takes ten times the volume of the solution as of the standard to produce an equivalent spot, then it is indicated that the concentration in the solution being tested is only 10% of that of .the standard... v

vdistilled o' and recovered -for reuse.

1l Example VI .Anaqueous solutionof 1.96 gramsugluconic acid and 0.72 gram acrylic acid Vas their sodium salts is treated as described in Example I toproduce the acetone bisulfite adduct and an acetone solution of the free organic acids. Soda analyses show 1.13 grams NaOH in the adduct and 0.07 gram NaOH in the acetone solution. Chromatograpliic analyses show that at least 90% of each acid is present in the acetone solution. In this instance the chromatographic method differs somewhat from that used in Examples I-V. The ammonium salts of the acids are resolved in an alcoholic ammonium carbonate solutionand are detected by spray reagents according to the method of A. I. Van Duuren, Rec. Trav. Chim. 72, 889 (1953).

Example VII An aqueous solution containing 8.8 grams of pyruvic acid as its sodium salt is concentrated to a volume of about 15 ml. and sulfur dioxide gas and 100 ml. of acetone is added. A small bottom layer having a syrupy consistency separates from solution. When the mixture is heated, syrup changes toa crystalline solid. The mixture is filtered and the solid is dissolved in 15 ml. of water. This aqueous solution is treated with 140 ml. of acetone and an excess of sulfur dioxide. The crystalline solid that forms is filtered. The combined acetone ltrates from the first and second filtration have a volume of 252 ml. Soda analyses show 3.76 grams NaOH in the `solid adduct and 0.24 gram NaOH inthe acetone. About 400 ml. of water is added to the acetone and the mixture is heated to distillout the acetone and sulfur dioxide. The aqueous residue is found to contain 2.73 grams or 31% of the pyruvic acid originally present.

Example VIII An aqueous solution containing 400 grams of sodium bisulte in a volume of 1200 ml. is added to two liters of concentrated kraft black liquor containing 31.6% solids. The mixture is heated to 90 C. with moderate stirring for `one hour and then liltered to separate the lignin precipitate from the solution. The Iltrate, which has a volume of 2750 rnl., is concentrated by evaporation to a volume of 1700 ml. and combined with one liter of methanol. The sodium sulte which precipitates is removed by iltration. The precipitate weighs 386 grams and contains 159 grams ysoda calculated as NagO. The filtrate is heated-to distill out the methanol and the aqueous residue is concentrated to 450 ml. This con- 'centrated aqueous solution is treated with 1200 rnl. of

acetone and an excess of sulfur dioxide. The solid acetone bisulfite addition product which forms -is removed by filtration, leaving an aqueous Aacetone solution of organic acids. An additional liter of acetone is used to wash the solid adduct. The solid adduct after washing has an air-dry weight of 606 grams and contains 110.5 grams of-NazO. The combined acetone filtrate and Wash contain only 4.8 grams NaZO. Acetone and sulfur dioxide are nrecovered from thissolution by distillation, leaving an aqueous solution that contains 17.2 grams formic acid, 10.8 grams acetic acid, 6.4 grams glycolic acid, and 13.3 grams lactic acid. The solid acetone bisultite addition product is dissolved in water. Some sulfur which is associated with the acetone bisultite addition product does Ynot dissolve and is separated from the solution by decantation. The solution is heated to boiling. The acetone is The residual aqueous solution contains sodium bisulte.

Example IX Aof concentrated kraft black liquor containing 31.6%

solids. The mixture is heatednto 90 C. with moderate stirring for one hour and then filtered to separate the 12 lignin precipitate from the solution. The filtrate, which has a volume of 2970 ml. is concentrated by evaporation. The solid sodium sulite which forms is'separated lfrom the solution by filtration. This precipitate weighs 360 grams and contains 168.3 grams soda calculated as NazO. The total volume of the iiltrate is 670 ml. It is determined that each rnl. of this solution contains 71 grams of water, 58 grams of solids, and has a soda content equivalent to 17.3 grams NazO. Treating this solution with acetone and sulfur dioxide gives results substantially the ysame as those described in Example VIII. However, in order to determine the eiiect of various ratios of water to acetone, a 100-ml. portion is treated directly with acetone and SO2 and, in three instances, 100-ml. portions of the solution are evaporated to remove part of the water prior to treatment with acetone and SO2. In every case, the aqueous solution is treated with 200 ml. of acetone and an excess of sulfur dioxide. The solid adduct is removed by filtration and analyzed for NazO content. The data which are summarized below show that under these conditions from 62 to 91% of the total soda in the solution is recovered in thesolid adduct:

Grams Grams Percent of Portion No. H10 Naz@ in Total i Adduct NanO In each case, the aqueous acetone and the solid adduct are processed as described in Example VIII and the results are substantially the same as are reported in that example.

Example X Sulfur dioxide is added to two liters of concentrated kraft black liquor containing 31.6% solids until the mixture is approximately neutral. The mixture is then heated to 90 C. for about an hour during which time there is considerable evolution of carbon dioxide gas. The mixture is then filtered to separate the lignin precipitate from the solution. The volume of the ltrate is reduced to 1260 ml. -by evaporation and 750 ml. of methanol is added. The sodium sulte which precipitates is removed by filtration. From a sodium analysis, -this precipitate is calculated to contain Igrams of sodium sultite. The aqueous methanol solution is processed in a manner and the results obtained are substantially the same as those described in Example VIII.

Example X I Five hundred ml. of black liquorconcentrated to 31.6 weight percent solids is autoclaved at a temperature of about 250 C. for one hour. The autoclaved liquor is combined with 83 grams of sodium bisulite in `solution in ml. of water, and filtered to remove lignin solids. Six hundred and thirty rnl. of filtrate containing 63.2 grams of sodium, calculated as sodium oxide, are recovered and concentrated to v350 ml. on a steam pot. One hundred m1. of acetone is added to the concentrated liltrate and the mixture is permitted to stand over night. The sodium sullite heptahydrate which precipitates is removed by tiltration to provide a cake weighing 122 grams wet and containing 28L4 grams of sodium oxide. Four hundredml. of ltrate containing 30.5 grams of sodium oxide 'are recovered, saturated at room temperature with sulfur dioxide, and extracted with 250 ml. of methyl ethyl ketone in a separatory funnel. The ketone layer comprises a methyl ethyl ketone solution of low molecular weight carboxylic acids including about 4.1 grams of acetic acid, 3.9lgrarns of lactic acid, 1.1 grams of glycolic acid, and 4L3 grams of a mixture of formic acid and alphahydroxybutyric acid, calculatedv as formic acid. The ketone layer was distilled in conventional manner to recover thel ketone which was recycled through the system.

The aqueous solution of ketone-sodium bisulte adduct is decomposed by heat to provide ketone as a distillate and an aqueous solution of sodium bisullte as a residue both of which are recycled through the system. It will be appreciated that the low molecular weight `carboxylic acids which are not recovered are retained in the system. Under ideal conditions, an equilibrium is reached where the quantity of such acids recovered equals or approaches that in the liquor employed as a starting material.

Analogous results are obtained when higher molecular weight relatively water immiscible ketones, as contemplated by the invention, are utilized in lieu of methyl ethyl ketone.

Example XII Seven hundred ml. of brown liquor from neutral sulte semichemical pulping concentrated to about 31.6% by weight solids are heated in an autoclave to a temperature of about 270 C. The autoclaved liquor is then combined with 165 grams of sodium bisultite in solution in 500 ml. of water, heatedto the boiling point to evolve carbon dioxide, and filtered hot to remove lignin solids. The liltrate, including wash water, totals 1390 ml. and contains 112 grams of sodium calculated as sodium oxide. 'Ihe ltrate is concentrated to 705ml. by the evaporation of water combined with 230 grams of acetone, and permitted to stand to effect precipitation of sodium suliite heptahydrate. A wet sodium sulte heptahydrate cake weighing 207 grams and containing 45 grams of sodium calculated as sodium oxide is removed by filtration. The filtrate is saturated with sulfur dioxide and thereafter extracted four times with 540 ml. of methyl ethyl ketone in a separatory funnel to provide a ketone extract or layer containing about 11.3 grams of acetic acid and small amounts of other low molecular weight carboxylic acids. The ketone layer is distilled to separate ,the ketones present therein from the carboxylic acid components. The aqueous layer, comprising a solution of methyl ethyl ketone-sodium bisulte adduct, is decomposed in the manner described in Example XII.

Example XIII Sulfur dioxide, in an amount requisite to lower the pH 4 to about 1.9 is introduced, in an absorption towerY into a 1000 ml. or 1 l. portion of concentrated brown liquor from a neutral sullite pulping process containing essentially all of the lignin materials originally present and 5 04 grams of total solids of which 98.6 grams is sodium calculated as sodium oxide. vThe liquor is then extracted six times in a separatory funnel with a total of 4.5 liters of methyl ethyl ketone. In each extraction two layers are formed and separated. The ketone layers are combined and distilled to recover methyl ethyl ketone therefrom.

The aqueous residue from the ketone distillation contains 36.4 grams of acetic acid.

The aqueous layer resulting from the ketone extraction contains the sodium bisulfite addition product of methyl ethyl ketone and lignin solids and is characterized by a pH of 2.4. About 148 grams-of sodium carbonate monohydrate is added to the aqueous layer to decompose the adduct after which m'ethyl ethyl ketone is separated by distillation and recovery. Separation of sodium sulte `14 with 100 ml. of acetone. -Sixteen grams of sulfur dioxide gas is then introduced. The reaction mixture forms a dark colored aqueous bottom layer and a lighter colored acetone-containing top layer. After about an hour the bottom layer is separated and filtered to remove theprecipitated acetone-sodium bisulite adduct which has a wet weight of 27.5 grams and an air-dry weight of 12.5 grams, and which is characterized by a sodium content, calculated as sodium oxide, of about 3.63 grams.

The filtrate is then treated with an additional 100 ml. of acetone and seventeen grams of sulfur dioxide in the manner previously described to yield a second portion of crude adduct having 4wet weightk of about 20 grams, an air-dry weight of about 11 grams, and al sodium content, calculated as sodium oxide, of about 3.72 grams. The combined amount of sodium in the two adducts accounts for about 52 weight percent ofthe sodium originally present in the brown liquor. The two acetone layers are combined and distilled to recover the acetone and provide an aqueous residue containing 2.5 grams of acetic acid, 0.6'gram of formic acid, 0.4 gram of lacticracid, and 0.2 gram of glycolic'acid.

Example XV Four mixtures of brown liquor from neutral sulte semichemical pulping and black liquor are prepared containing 10%, 20%, 30%, and 40% by weight brown liquor solids. All mixtures are adjusted to contain about 350 grams of total solids in a total volume of about 700 ml. The mixtures are prepared by mixing dilute black liquor containing about 18% `by weight solids and dilute brown liquor containing about 9.5% solids inpropor.- tions requisite to produce the desired percentage of brown liquor solids and the mixture concentrated in a long tube evaporator by which from about 1.5 to about 2 liters of water, as required, are removed. v

Each of the 700 m1. samples is pressure cooked in an autoclave to a temperature of about 270 C. and thereafter filtered to remove precipitated ligninV solids.k To each of the filtrates is added 100 to 110 grams of NaHSO3 dissolved in about 275 ml. of H2O. The mixture is heated to expel CO2 and an additional lignin solids precipitate is removed. The essentially neutral ltrates resulting are concentrated by evaporation to about 700 ml. and mixed with about 250 ml. of acetone. The mxturevis maintained at room temperature for about minutes to precipitate sodium sulte heptahydrate, which is separated. The sodium sulte heptahydrate product is of good quality and is obtained in each case in about 30% to about 35% yield based on the total quantity of sodium oxide present. The acetone is employed in an amount requisite only to effect the desired sodium sultite heptahydrate precipitation. y

In each sample, the liquor from which the sodium suliite heptahydrate is recovered is saturated with sulfur dioxide. and extracted with'methyl ethyl ketone to form from the residual portion ofthe aqueous layer is complil cated by reason of theviscosity occasioned by lignin fonate materials present therein.

Example Xl V Brown liquor from a neutral sullite pulping process containing a solids content of 9.5 by weight is concentrated to a solids content of about 44% by weight. One hundred ml. of concentrated brown liquor containing about 54 grams of solids and including about 13.1 grams of sodium, calculated as Na2O, together with substantially sulall-fof the lignin materials originallyL present-'is-combined a liquid phase containing the low molecular weight organic acids. The ketone-sodium bisullite adduct is present in an essentially aqueous solution. The acid-containing liquid phase is separated and processed to obtain an organic acid product, and acetone and methyl ethyl ketone for recycle. The adduct phase is decomposed by heat to provide ketones and sodium bisulite for recycle.

The electof increasing the brown liquor solids content on the organic product is shown by the acid content of the ketone phase obtained from the four mixtures as tabulated below.

Percent Brown Liquor Solids Acetlc Formic yLaetie Glycolic Acid (g.) (g. (g.) (g.)

Example XVI Seven thousand four hundred and fty-ve parts by weight of brown liquor containing about 42.9% solids and a total of about 81 grams of sodium oxide are autoclaved in nine separate batches for a period of about thirty minutes each at a temperature from about 275 to 280 C. at an average maximum pressure of 1700 p.s.i. The autoclaved liquor in the form `of a Vblend of the nine separate batches is carbonated with .carbon dioxide for a time period requisite to expel essentially all of the hydrogen sulde and thereafter reacted with sulfur dioxideto a pH of about 2 and the lignin solids precipitate is removed by filtration. The filtrate is treated with methyl ethyl ketone in an amount suiiicient to react with the sodium bisuliite present and to saturate the solution. After completion of the reaction the mixture is cooled and a small amount of a precipitate, identified as a mixture of sulfur and the adduct of methyl ethyl ketone and sodium bisultite, is separated.

The vliquor totals 7000 ml. and is then extracted with a total of 5950 ml. of methyl ethyl ketone in a ivestage extraction simulating a continuous countercurrent process. The extraction eiciency for acetic acid is about 92%.

The extracted aqueous phase is slowly added to boiling sodium carbonate solution to effect removal of the methyl ethyl ketone present by distillation and conversion of the sodium bisulte to sodium sultite. The resulting reaction mixture is characterized by a pH of about 8 and is then evaporated to affect precipitation of about 1270 grams of a sodium suliite product.

The methyl ethyl ketone extract is distilled in a Stedman column to separate water and methyl ethyl ketone from the essentially acetic acid product.

After a forerun up to about 115 C. the distillate came over at a constant temperature of about 115 C. to provide a center cut of 161 grams which analyzes as acetic acid of about 98 to about 99% purity, which is purified by redistillation.

This application is a continuation-impart of Sandborn et al. application, Serial No. 584,458, for Recovery of Soda from Organic Acids, tiled May 14, 1956, now abandoned, and Sandborn et al. application, Serial No. 584,459, for Chemical Recovery Process, filed May 14, 1956, now abandoned. Reference is also made to Sandborn et al., Serial No. 584,460, for Chemical Recovery Process, filed May 14, 1956.

We claim:

l. The process which comprises reacting in an aqueous solution, an alkali metal salt of at least one aliphatic nonaldehydic carboxylic acid having from` one to three carbon atoms per molecule with (l) bisultite ion, and (2) a normally'liquid aliphatic ketone capable of forming an alkali metal bisuliite adduct to produce a first-phase containing said carboxylic acid and a second phase containing an alkali metal bisullite adduct of said ketone, said alkali metal of said adduct being derived from said carboxylic acid salt, and separating said'lirst and second phases said ketone having a. formula selected from the group consisting of and and said adduct having a formula selected from the group consisting of R1 R-OoH and SOQM

R and R1 in said formulae representing aliphatic radicals, R2 in said formulae representing an aliphatic radical which formsa cyclic compound with the carbon atom and M in said formulae representing an alkali metal atom.

2. The process of claim l wherein said ketone contains from about `three to about six-carbon atoms per molecule.

3. The process of claim l wherein said ketone is selected from the group consisting of acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-isopropyl ketone, methyl-isobutyl ketone, cyclohexanone and mixtures thereof. x

4. The process of claim 1 wherein said ketone is acetone.

` 5. The process of claim l wherein'said ketone is methyl ethyl ketone.

6. The process of claim 1 wherein said alkali metal salt of an aliphatic nonaldehydic carboxylic acid is a sodium salt.

7. The process of claim l wherein said phase containing said adduct is heated to distill ketone therefrom and provide a residue comprising an alkali metal bisulte.

8. The process of claim l wherein saidphase containing said adduct is reacted with an alkali metal carbonate to produce an alkali metal suliite.

9. A process forV producing sodium bisulte from a sodium salt of an aliphatic, nonaldehydic, water-soluble, carboxylic acid which comprises reacting said salt in aqueous solution with acetone and sulfur dioxide to produce a reaction mixture including an aqueous acetone solution of free acid liberated from said salt and an acetone-sodium bisulfite additionproduct precipitate, separating Vsaid addition product precipitate from said solution, `and recovering sodium bisulte from said addition product.

10. The process which comprises reacting aused pulping liquor selected from the group consisting of used alkaline pulping liquors and used neutral pulping liquors, which contains an alkali metal salt of a saturated monocarboxylic acid having from one to three carbon atoms per molecule with bisuliite ion and a normally liquid aliphatic ketone having from about three to about six carbon atoms and capable of forming an alkali metal bisulite adduct to produce (a) a first phase containing said carboxylic acidsand (b) a second phase containing an alkali sodium metal bisulfite adduct of said ketone, said alkali metal of said adduct being derived from said carboxylic acid and separating said phases said ketone hav- `ing a formula selected lfrom the group consisting of R--Rl and Rgr-O V.

and said adduct having ahformula selected from the which forms a cyclic compound with the carbon atom and M in said formulae representing an alkali metal atom,

l1. The' process of claim 10 wherein said ketone is acetone.

12. The process of claim 10 wherein said ketone is methyl ethyl ketone.

13. A process for producing a nonaldehydic, carboxylic acid containing from one to about four carbon atoms from a used pulping liquor selected from the group consisting of used alkaline pulping process liquors and used neutral pulping process liquors containing alkali metal salts of a nonaldehydic carboxylic acid containing from about one to about four carbon atoms, which comprises removing a substantial portion of the lignin materials present insaid liquor, reacting the deligniiied liquor with a material selected from' the group consisting of sulfur dioxide and sulfurous acid to produce sodium suliite, recovering said sodium sulite, and thereafter reacting said liquor with bisuliite ion and an aliphatic ketone capable of forming an alkali metal bisulite adduct to provide (a) a iirst phase containing -said carboxylic acids and (b) a second phase lcontaining an alkali metal bisulte addition product of said ketone and separating said phases said ketone having a formula selected from the group consisting of Il R-C-B1 and and said adduct having a formula selected from the group consisting of /Rx R-C-OH SoaM and R and R1 in said formulae representing aliphatic radicals, R2 in said formulae representing an aliphatic radical which forms a cyclic compound with the carbon atom and M in said formulae representing an alkali metal atom.

14. The process of claim 13 wherein said used pulping liquor is black liquor from an alkaline pulping process.

15. The process of claim 14 wherein said black liquor is subjected to heat and pressure to eiiect removal of a substantial portion of the lignin materials present therein.

16. The process of claim 14 wherein said black liquor is concentrated to a solids content of at least about twenty ve weight percent.

17. The process of claim 16 wherein a material selected from the group consisting of sulfur dioxide and sulfurous acid is introduced into said concentrated black liquor to eifect precipitation of lignin materials and produce sodium suliite.

18. The process of claim 17 wherein said delignied black liquor is commingled with a material selected from the water miscible aliphatic alcohols and ketones in which sodium suliite is insoluble to effect precipitation of said sodium sulfite.

19. The process of claim 18 wherein said deligniiied black liquor is commingled with acetone to precipitate sodium suliite heptahydrate.

20. The process of claim 19 wherein said delignified black liquor after separation from said sodium sulte heptahydrate precipitate, is reacted with bisulite ion and a substantially water immiscible aliphatic ketone containing from about four to about six carbon atoms to provide a first, essentially ketone, phase containing free nonaldehydic aliphatic carboxylic acids and a second essentially aqueous phase comprising a water solution of ketonesodium bisuliite adduct. Y

21. The process of claim 13 wherein said used pulping `liquor is from a neutral pulping process.

22. The process of claim 21 wherein -said used pulping liquor is concentrated to at least about twenty iive weight percent.

23. A process which comprises reacting a sodium salt `of an aliphatic non-aldehydic, water-soluble, carboxylic acid in aqueous solution with acetone and sulfur dioxide to produce a reaction mixture including an aqueous acetone solution of free acid liberated from said salt and an acetone-sodium bisuliite addition product precipitate, and separating said addition product precipitate from said acid solution.

24. The process of claim 23 wherein said addition product is dissolved in water and heated to distill acetone therefrom to effect recovery of sodium bisulte in an aqueous solution. v

25. The process of claim 23 wherein said acids cornprise monobasic acids.

26. The process or" claim 23 wherein said acids comprisepolybasic acids.

27. The process of claim 23 wherein said acids comprise hydroxy acids.

28. The process of claim 23 wherein said acids comprise keto` acids.

29. The process which comprises reacting a concentrate, resulting from an aqueous alkaline cook of cellulosic material and containing sodium salts of saturated monocarboxylic acids having from one to three carbon atoms per molecule, with acetone and a material selected from the group consisting of sulfur dioxide and sulfurous acid to produce (a) an aqueous acetone solution of said acids and (b) a precipitate of an acetone-sodium bisulte addition product and separating said addition product from said acid solution, there having been removed from said concentrate prior to said reaction a substantial portion of the lignin normally present therein.

30. The process of claim 29 wherein acetone is recovered from said separated addition product.

31. The process of claim 30 wherein at least a portion of said separated acetone is recycled to reaction with said concentrate.

32. The process of claim 29 wherein said material With which said concentrate is reacted comprises sulfur dioxide.

33. The process of claim 29 wherein said material with which said concentrate is reacted comprises sulfurous acid.

34. The process of claim 29 wherein the sodium salts present in said liquor comprise the sodium salts of alphahydroxy saturated monocarboxylic acids having from one to three carbon atoms per molecule.

3S. The process which comprises removing a substantial portion of the lignin from a concentrate of liquor resulting from an aqueous alkaline cook of cellulosic material and containing sodium salts of saturated monocarboxylic acids having from one to three carbon atoms per molecule, reacting the delignified concentrate with acetone and a material consisting of sulfur dioxide and sulfurous acid to produce a reaction mixture including an aqueous acetone solution of saturated monocarboxylic acids having from one to three carbon atoms per molecule, and a precipitate of an acetone-sodium bisulte addition product, and separating said addition product from said solution.

36. The process of claim 35 wherein said lignin is precipitated from said concentrate by the addition of a precipitant selected from the group consisting of sodium bisulte and sulfur dioxide, and the precipitate so formed is removed.

37. A process which comprises concentrating a used pulping liquor selected from the group consisting of used alkaline pulping liquors and used neutral pulping liquors containing alkali metal salts of nonaldehydic aliphatic carboxylic acids from one to about four carbon atoms to a solids concentration of at least about twenty-tive percent by weight, introducing a material selected from the group consisting of sulfur dioxide and alkali metal bisulte into said concentrated liquor to precipitate `lignin solids and form sodium sulfite, removing said lignin solids, recovering sodium suliite from said concentrated delignied liquor andthereafter reacting said liquor with bisullite ion and acetone to produce (a) a first phase containing nonaldehydic aliphatic carboxylic acids containing from one to about four carbon atoms derived from said liquor and (b) a second phase containing an acetone sodium bisulte addition product, and separating said phases.

38. A process which comprises concentrating a used pulping liquor selected from the group consisting of used alkaline pulping liquors and used neutral pulping liquors containing alkali inetd salts of nonaldehydic aliphatic carboxylic acids from one to about four carbon atoms to a solids concentration of at least about twenty-five percent by weight, introducing a material selected from the group consisting of sulfur dioxide and alkali metal bisultite into said concentrated liquor to precipitate lignin solids and form sodium sulte, removing said lignin solids, re-

covering sodium sulfite from said concentrated delignied liquor and thereafter reacting said liquor with bitsulte ion a'nd methyl ethyl ketone to produce (a) a first phase containing nonaldehydic aliphatic carboxylic acids containing from one to about four carbon atoms derived from said liquor and (b) a second phase containing a methyl ethyl ketone sodium bisuliite addition product, and separating said phases. n

39. The process of claim 38 wherein said concentrated deligniled sodium sulte-containing liquor is mixed with acetone to precipitate sodium suliite as the heptahydrate.

OTHER REFERENCES Feisor and Feisorz Organic Chemistry, 2nd edition, pp. 203-5 (QD 25l/F5, 1950). 

1. THE PROCESS WHICH COMPRISES REACTING IN AN AQUEOUS SOLUTION AN ALKALI METAL SALT OF AT LEAST ONE ALIPHATIC NONALDEHYDEIC CARBOXYLIC ACID HAVING FROM ONE TO THREE CARBON ATOMS PER MOLECULE WITH (1) BISULFITE ION, AND (2) A NORMALLY LIQUID ALIPHATIC KETONE CAPABLE OF FORMING AN ALKALI METAL BISULFITE ADDUCT TO PRODUCE A FIRST-PHASE CONTAINING SAID CARBOXYLIC ACID AND A SECOND PHASE CONTAINING AN ALKALI METAL BISCULFITE ADDUCT OF SAID KETONE, SAID ALKALI METAL OF SAID ADDUCT BEING DERIVED FROM SAID CARBOXYLIC ACID SALT, AND SEPARATING SAID FIRST AND SECOND PHASES SAID KETONE HAVING A FORMULA SELECTED FROM THE GROUP CONSISTING OF 